A pantograph is a simple machine that came along quite late. I can imagine a similar machine for carving, but I think it's quite easy to view the past with our own perspectives. The pantograph, and this speculative carving machine, are labor saving devices. I assume the Minoan sealstones were custom-made, one-of-a-kind items for those important enough to use them. While labor was cheap in most cases, those in need of this specialized skill were able to pay the cost.